Halogenation and dehydrochlorination of straight chain alkanes using an aromatic diluent



United States Patent HALOGENATION AND DEHYDROCHLORINATION 0F STRAIGHT CHAIN ALKANES USING AN AROMATIC DILUENT Louis L. Ferstandig, El Cerrito, and Jonas P. Harrison,

Pinole, Califi, assignors to Chevron Research Company, a corporation of Delaware N0 Drawing. Filed Dec. 2, 1963, Ser. No. 327,518

4 Claims. (Cl. 260-677) This invention concerns the dehydrochlorination of aliphatie monochloride hydrocarbons. More particularly, this invention concerns the dehydrochlorination in the vapor phase of monochlorinated aliphatic hydrocarbons of at least 9 carbons.

Recently, much publicity has been. given to the biodegradability of synthetic detergents. The highly branched alkylbenzene sulfonates (ABS), particularly tetrapropylene benzene sulfonate, are the synthetic detergents around which concern is mostly centered. The problem of biodegradability can be significantly ameliorated by using a straight-chain alkylbenzene sulfonate (SCABS).

One route to SCABS from alkanes is to chlorinate the alkane to a monochloro product, catalytically dehydrochlorinating the monochloro product to an olefin over a dehydrochlorination catalyst, and then catalytically alkylating benzene with the olefin.

It is found that in .the alkylation subsequent to dehydrochlorination the product obtained has significant amouts of material, which ultimately appears in sewage tests as non-biodegradable or hard core. The amount of hard core must be minimized. Preferably, it should be 2% or less for a satisfactory product.

It has now been found that the non-biodegradable hard core can be significantly reduced by using an aromatic hydrocarbon as a diluent during the elimination of hydro gen chloride over conventional solid acidic dehydrochlorination catalysts.

The alkyl chlorides are of from about 9 to 20 carbons, more usually of from about 11 to 14 carbons. While a single alkane can be used, more usually mixtures of alkanes are employed. Free radical catalyzed liquid phase chlorination is used, chlorinating to about 15 to 35 mole percent, in order to minimize the amount of polychlorinated hydrocarbon; this results in carrying along during the process, as an inert diluent, the non-chlorinated alkane (65-85%).

Solid acidic dehydrochlorination catalysts are well known in the art, e.g., chromia-alumina, silica-alumina, etc. Among the acidic catalysts, chromia-alumina is preferred.

The aromatic hydrocarbons are of from 6 to 8 carbons, i.e., benzene, toluene and o-, m-, and p-xylenes; benzene is preferred.

The amount of aromatic hydrocarbon used is in the range of about 35-65 volume percent of the total volume of the mixture (this includes both a'lkane, if present, and alkyl chloride in addition to the benzene). Preferably, the amount of aromatic hydrocarbon will be in the range of about 45 to 55 volume percent.

The temperature used for the dehydrochlorination will be ,at least the vaporization temperature of the highest boiling chlorohydrocarbon, usually 550 F., and will rarely exceed 800 F. More usually, the temperature range will be from about 550 to 700 F.

The space velocity is not critical and will generally be in the range of about /2 to 100 LHSV in volume per volume per hour. More usually, it will be in the range of about 1 to 25 volume per volume per hour. The process is most convenient as a continuous process in which the vapors of aromatic hydrocarbon, the chloroalkanes and, when present, alkane, are passed over the hot catalyst ICC continuously. The reaction mixture is fed into a reaction zone at a temperature which instantly vaporizes the mixture, the vapor passes over the acidic dehydrochlorination catalyst, is dehydrochlorinated and then condensed; the condensed mixture is washed with water or conventional bases to remove residual hydrogen chloride and then dried by any convenient means.

The following examples are offered by way of illustration and not by way of limitation.

APPARATUS A 21 mm. inner diameter tube or a A inch tube held in a vertical position was filled with catalyst particles held in place by a grid. At the bottom of the tube was a condenser and a gas separator. The feed was pumped into the top of the tube, vaporized in a preheat section, and filled with inert Alundum, and then passed through the catalyst bed. The HCl which formed was removed in the separator at the reactor outlet. The reaction was equipped with pressure regulating equipment maintained at 1-10 pounds p.s.i.g. and was heated by means of an external electric furnace surrounding the reactor tube.

Example 1 The apparatus described above was charged with a chromia-alumina catalyst (Houdry A and C). A feed stock was prepared by chlorinating a straight-chain paraffin mixture containing about equal amounts of undecane, dodecane, tridecane and tetradecane to a mixture having 4.7% by weight of chlorine. The mixture had a density of 0.787 gram per cc. and a refractive index of 1.4298 at 25 C.

The chlorination was thermally initiated at about F. It took place in a 300 gallon glass lined kettle with the reaction taking about 1 to 2 hours. The kettle was jacketed and steam was used as a heat source. At the end of the reaction, the mixture was purged with nitrogen and cooled.

The catalyst bed was heated to 580 F. and the above mixture pumped over the catalyst at 3 ml. per hour per ml. of catalyst volume at atmospheric pressure. The resulting olefin-paraliin product had a density of 0.759, contained 0.12% by weight of chlorine, and had a refractive index of 1.4275. The feed .had a content of other than normal aliphatic hydrocarbon of 6% and the product 10%.

An alkylbenzene was prepared by alkylating benzene with the above-described crude olefin mixture in the presence of hydrogen fluoride. A 1:10:10 mole ratio of olefin to benzene to HF was used. The alkylation was done batchwise at 40-60 F. The HF phase was removed, the hydrocarbon layer washed with 20% KOH, phase separated and :distilled. The resulting straight-chain alkylbenzene was separated from unreacted benzene and paraffin by distillation. The product had a density of 0.86 gram per cc. and an index of refraction of 1.4837 at 25 C.; it boiled in the range of 533 to 665 F. The product was sulfonated with oleum to give an alkylbenzene sulfonate (ABS) detergent.

The ABS detergent formed in this manner was essentially biologically soft (i.e., destroyed by a bacterial action) except for about 4%, which was unaffected in a usual laboratory sewage treatment. The procedure used for testing is described in R. House and B. A. Fries, Sewage and Industrial Wastes, 28 492 01956).

Example 2 The above-described reactor was charged with chromiaalumina catalyst (Oronite XRB-fi) and heated to 650 F. The feed stock, a straight-chain chloroparaflin containing 4.83% by weight of chlorine was prepared by partially chlorinating a C -C n-pa-raflin mixture containing 6% of other than normal aliphatic hydrocarbons. The partially chlorinated mixture was diluted with an equal weight of benzene. This mixture was 'fed to the reactor at 3 ml. per hour per g. of catalyst. The product had a content of other than normal aliphatic hydrocarbons. The product was treated as described in Example :1 to obtain the ABS detergent. The material from this example contained only about 2% by weight of detergent which was unaffected by a laboratory sewage treatment.

By carrying out the dehydrochlorination in the presence of benzene, an olefin is obtained which produces an alkylbenzene detergent of 50% greater biological softness (i.e., the amount of hard core detergent is reduced by half).

Example 3 A synthetic mixture of 13% l-decylchloride in normal dodecane was dehydrochlorinated at essentially the same conditions as in Example '1. The feed contained '0J13% of other than normal aliphatic hydrocarbons, the product 1.9%.

Example 4- The reaction was carried out essentially the same as Example 3, except with 50% by weight of benzene. The product contained 0.6% of other than normal aliphatic hydrocarbons.

Example 5 The reaction was carried out essentially the same as Example 4, except that the benzene diluent was replaced by n-hexane. The product was found to have 3% of other than normal aliphatic hydrocarbons. n-Hexane was, therefore, found to have no efieot.

As will be evident to those skilled in the art, various modifications on this process can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the, disclosure or from the scope of the following claims.

We claim:

1. In a process for preparing olefins to be used in the preparation of straight-chain alkylbenzene sulfonates substantially free of non-biodegradable material, which comprises dehydrochlorinating monochloro normal alkanes of from 9 to 20 carbons with an acidic dehydrochlorination catalyst at a temperature in the range from at least the vaporization temperature of the highest boiling monochloroalkane to 800 F. at a liquid hourly space velocity of from about /2 to 100 volume per volume per hour, the improvement which comprises diluting the chloroalkanes with an aromatic hydrocarbon of from 6 to 8 carbons to a total volume containing from about at least 35 volume percent of said aromatic hydrocarbon.

2. In a process for preparing olefins to 'be used in the preparation of straight-chain alkylbenzene sulfonates substantially free of non-biodegradable material, which comprises chlorinating a mixture of alkanes of from 9 to 20 carbons to about 15 to 35 mole percent conversion, and then dehydrochlorinating the resulting mixture over an acidic dehydrochlon'nation catalyst at a temperature in the range from at least the vaporization temperature of the highest boiling chlorohydrocarbon to 800 F. at a liquid hourly space velocity of from about A; to 100 volume per volume per hour, the improvement which com prises diluting the alkane-chloroalkane mixture with aromatic hydrocarbons of 6 to 8 car-bons to a total volume containing from about 35 to volume percent of arcmatic hydrocarbons.

3. In a process for preparing olefins to be used in the preparation of straight-chain alkylbenzene sulfonates substantially free of non-biodegradable material, which comprises chlorinating a mixture of alkanes of from 9 to 20 carbons to about 15 to 35 mole percent conversion, and then dehydrochlorinating the resulting mixture over an acidic dehydrochlorination catalyst at a temperature in the range from at least the vaporization temperature of the highest boiling chlorohydrocarbon to 800 F. at a liquid hourly space velocity of from about /2 to I volume per volume per hour, the improvement which comprises diluting the alkane-chloroalkane mixture with .benzene to a total volume containing from about 35 to 65 volume percent of benzene.

4. A method according to claim 3, wherein the temperature is in the range of from about 500 to 700 F. and the volume percent of benzene is in the range of from about 45 to 55.

References Cited by the Examiner UNITED STATES PATENTS 2,065,323 12/1936 Thomas et al. 260677 2,164,334 7/1939 Marks 260-677 2,563,050 8/1951 Linn et a1. '2'60663 ALPHONSO D. SULLIVAN, Primary Examiner. 

1. IN A PROCESS FOR PREPARING OLEFINS TO BE USED IN THE PREPARATION OF STRAIGHT-CHAIN ALKYLBENZEN SULFONATES SUBSTANTIALLY FREE OF NON-BIODEGRADABLE MATERIAL, WHICH COMPRISES DEHYDROCHLORINATING MONOCHLORO NORMAL ALKANES OF FROM 9 TO 20 CARBONS WITH AN ACIDIC DEHYDROCHLORINATION CATALYST AT A TEMPERATURE IN THE RANGE FROM AT LEAST THE VAPORIZATION TEMPERATURE OF THE HIGHEST BOILING MONOCHLOROALKANE TO 800*F. AT A LIQUID HOURLY SPACE VELOCITY OF FROM ABOUT 1/2 TO 100 VOLUME PER VOLUME PER HOUR, THE IMPROVEMENT WHICH COMPRISES DILUTING THE CHLOROALKANES WITH AN AROMATIC HYDROCARBON OF FROM 6 TO 8 CARBONS TO A TOTAL VOLUME CONAINING FROM ABOUT AT LEAST 35 VOLUME PERCENT OF SAID AROMATIC HYDROCARBON. 